The present invention relates to a method and apparatus for continuously heating an advancing yarn, and more particularly, to a method and apparatus for producing a highly oriented yarn as part of a melt spinning operation.
Yarn heating tubes are conventionally employed in melt spinning operations, wherein a polymeric melt is extruded through a plurality of orifices of a spinning die so as to produce a plurality of filaments, which are then cooled and gathered together to form a yarn composed of a bundle of solidified filaments. The advancing yarn is then heated by passing the yarn through a tubular heating tube.
The dwell time of the yarn in the heating tube is of significance in achieving desired yarn properties, such as strength, elongation behavior, and shrinking behavior. Since the advancing speed is a given, the heating tube must be exchanged for a tube of a different length, in order to vary the dwell time for adapting the system to a yarn of pre-existing properties, such as the polymer of the yarn, the total denier of the yarn, and the denier of the individual filaments.
It is accordingly an object of the present invention to provide a method and apparatus for heating a yarn in a process of the described type, and which avoids the necessity of exchanging the heating tubes to achieve desired yarn characteristics under varying conditions.
It is a more particular object of the present invention to provide a method and apparatus for heating a yarn which is characterized by the ability to vary the dwell time of the yarn in a heating tube at a given yarn speed, and without exchanging the heating tube.
It is a further object of the present invention to provide a method and apparatus of producing a highly oriented yarn as part of a melt spinning operation and which has provision for adjusting the parameters of the process so as to permit the process to be adapted to the pre-existing yarn properties.